In cellular communication, mobile radios (i.e. "radio") and radio base stations (i.e. "base") exchange data and control signals. The base can serve more than one radio, and several bases can serve a plurality of radios in a defined geographic area. A single radio generally communicates with one base at a time. The radio and base need to be time synchronized in order for the transmitted and received signals to be properly interpreted by the radio and the base.
In both radio and base there are timing units for timing events executed within the radio and the base. Such timing units can include one or more counters. The counters are used to time various events occurring within the radio and base and for measuring time intervals. For example, one counter can count the number of communication frames being exchanged between base and radio, and another counter can be used to trigger events that occur within a communication frame.
When a radio does not transmit or receive communication frames, and when there are no events to be triggered, the timing unit of the radio and other parts of the radio are halted. The radio timing unit and other parts of the radio exit their halt mode when the radio receives new communication frames or when there is a need to execute or trigger events within the radio. The exact time at which a radio timing unit exits a halt state or the exact time at which the timing unit is first started is usually not synchronized with the beginning of a communication frame which is received by the radio, causing a non-deterministic operation of the radio, and a complication in software used to control the radio.
Another disadvantage of the prior art result from the need to control the shutting-down procedure solely by the control unit. When a halt status results in shutting down non-vital elements within the radio, the control unit has to check if the timing unit has finished timing events, before closing non-vital elements. The control unit can not check the timing unit status constantly, because it has to control other elements of the radio. For the reasons mentioned before, a time lapse between the moment in which non-vital elements can be closed and the moment in which the control unit checks the status of non-vital elements can occur. The energy that is consumed by the non-vital elements, during this time lapse is wasted. Prior art apparatus also cause complications in software.
A further disadvantage of prior art apparatus is that the control unit must deal with the interaction between itself and timing unit, adding a load on said control unit.
A still further disadvantage of the prior art arrangement is the usage of a single, high frequency clock, during the operation of the radio and also during its halt status. The timing unit receives a high frequency clock, which is required for the radio operation. The high frequency clock is not needed during the halt mode, and its usage causes a high energy consumption.
Accordingly, there is a continuing need for improved methods and apparatus for handling radio halt operation, and exiting halt status.